When my students are feeling warm and good and happy after a class, I jokingly ask if they feel like they've just had a tune-up and oil change. In fact, while yoga doesn't change any fluids, it does do a wonderful job of moving fluids around in your body. Your blood circulates in your arteries and veins, and your lymph flows through the spaces around all your cells; both fluids can be cleansed of metabolic byproducts and your blood replenished with oxygen and nutrients. Yoga also helps circulate the synovial fluid inside your joints, but—contrary to common perception—it doesn't warm up or stimulate the manufacture of this important substance.
So what is synovial fluid? And if yoga helps move it around, what effect does that have on your health and mobility?
Understanding Synovial Fluid
Synovial fluid is the slippery fluid that fills most of the body's joints. All joints occur where two separate bones intersect or overlap, but there are a few that don't contain synovial fluid and have very limited movement, including the intervertebral (between the vertebrae) discs and the two sacroiliac joints on the back of the pelvis. The rest are synovial joints, which are freely movable and need a system that cushions the ends of the bones, allowing them to glide over each other without friction. This system consists of hyaline cartilage, the smooth, whitish covering on the ends of the bones, and the synovial fluid, which fills the space between the cartilage surfaces and facilitates smooth, painless movement between bones. This clear, slightly viscous fluid is also important because it delivers nutrients and oxygen to the hyaline cartilage, which—unlike most body tissues—doesn't have its own blood supply. Any joint movement helps circulate the synovial fluid, which feeds the cartilage; practicing yoga poses therefore helps keep the cartilage well-nourished.
Each synovial joint has a fibrous capsule surrounding the joint, which helps hold the bones together, along with the ligaments (which join bone to bone) and tendons (which join muscle to bone). The joint capsule is lined by the synovial membrane, which manufactures the synovial fluid. Your body automatically produces the necessary amount of this lubricating fluid. Although the idea that yoga stimulates production of synovial fluid creates a lovely image, there actually isn't any time when the well runs dry.
Inflammation: How Much Synovial Fluid Is Too Much
In fact, the only problem with the amount of synovial fluid occurs when there is too much. This problem is part of the inflammatory process, which is defined by the presence of swelling, pain, redness, and heat. Inflammation is the body's response to injury, as well as part of the process of arthritis, which includes the wearing away of hyaline cartilage. (In more advanced cases of osteoarthritis—the wear-and-tear arthritis commonly associated with old age—and in rheumatoid arthritis—the autoimmune disease in which the body attacks its own joint tissues—the synovial membrane also becomes painfully inflamed, and the cartilage can wear away until bone rests painfully on bone.)
Because increased synovial fluid production—we see it as swelling—is associated with injury and inflammation, you don't want your yoga practice to stimulate this production. In fact, we teachers should encourage students to practice in such a way that, over the months and years, their joints become healthier and stronger, and that they avoid strain and injury. One of the best ways to avoid joint damage is to teach students to pay attention to any pain in or directly around a joint, and to modify or change the alignment of the pose to eliminate that pain. Pain in or around a joint means one of two things: You are overstretching connective tissue, such as tendons and ligaments (which are designed to stabilize joints and will cause a joint to become hypermobile if overstretched); or you are compressing the joint surfaces, which can contribute to arthritis. So "no joint pain" should be your teaching rule. Leave the work on joints to trained health care professionals who know whether, and precisely how, to improve joint mobility without damaging the joint's cartilage or support system.
On the other hand, what should a teacher do if a student arrives at class with an already inflamed joint? A common example is a sprained ankle, which is painful, swollen, hot, and may be red. Ankle ligaments are often violently overstretched by stepping in a hole or slipping off a high heel, but any joint can become inflamed by damage to a ligament or tendon. Common examples are tears, which are often associated with accidents and athletic activities, and overworking a joint beyond its current level of condition. Overworking a joint to the point of inflammation can occur while doing yoga, perhaps by repetitively practicing a pose in incorrect alignment and thereby putting strain on ligaments or tendons. Also, seriously deconditioned or even atrophied shoulder muscles, for example, can easily be overworked by even a few Sun Salutations. And arthritis, of course, provides joint conditions that are easily provoked into inflammation.
How Yoga Can Circulate Synovial Fluid
The bottom line here is that an inflamed joint should never be pushed, stretched into pain, or worked vigorously, because the risk of increasing or prolonging the inflammation is great. It's much better to train your students to respond to the inflammation in a way that promotes health. Use the example of a sprained ankle to guide your problem solving. A sprained ankle is usually stabilized with a wraparound bandage, brace, or, in severe cases, even a cast. These stabilizers prevent movement, allowing the strained tissues to heal without disturbance. But if, instead, you move and stretch and work an inflamed joint, you'll likely cause repetitive microtrauma, which disrupts the healing process and may actually cause more damage.
So when dealing with inflammation, encourage your student to work vigorously on other parts of the body, and to choose poses that keep the inflamed joint relatively quiet until the pain and swelling have receded significantly. This is not to say you shouldn't move the joint at all: Mild, unforced movements help the healing process by circulating the blood to ligaments, tendons, and muscles, and by circulating synovial fluid to hyaline cartilage. However, if the inflammation or pain is severe, or the problem is showing no improvement or is even getting worse, urge your student to see a health care provider to evaluate the problem, run necessary tests, and prescribe a treatment plan.
About Our Expert
Julie Gudmestad is a certified Iyengar Yoga teacher and licensed physical therapist who runs a combined yoga studio and physical therapy practice in Portland, Oregon.